Transmission chains are applied quite commonly, but no report on unidirectionally bendable transmission chains has been disclosed so far.
Trafficability at grade crossings of a city is an important part of city traffic. In order to ensure traffic safety at the grade crossings of the city, besides the provision of complete traffic signaling facilities, manual management is often combined. An important issue of the manual management is to instruct pedestrians at an entrance of a pedestrian crossing to pass in order according to the traffic signals. However, the situation where the pedestrians do not obey the instruction often happens, and then roadblocks are accordingly set up to prevent the pedestrians from violating regulations to pass at will. The corresponding facilities further include roadblocks set up at entrances of some venues to make it convenient to manage vehicles and pedestrians.
There are various types of roadblocks in the prior art, including a translational roadblock, a rotary roadblock, a hydraulic roadblock and the like. Among others, the translational roadblock and the rotary roadblock each occupy too much space at an intersection which is already confined, and they require a lot of time to reach their positions, which prolongs the passing time; and in the case of the hydraulic roadblock, there is a need to establish a hydraulic station and oil pipes, which also occupy a large space and are required to be installed and maintained frequently, with a high cost.